is an online news and social networking service where users post and read messages restricted to 140-characters, which are called “tweets”. Registered users can post and read tweets, but those who are unregistered can only read them. Users access Twitter through the website interface, SMS or mobile device app.
As a social network, Twitter revolves around the principle of followers. When you choose to follow another Twitter user, that user’s tweets appear in reverse chronological order on your main Twitter page. If you follow 20 people, you’ll see a mix of tweets scrolling down the page: breakfast-cereal updates, interesting new links, music recommendations, even musings on the future of education.